During the time of the Taiping Rebellion (1850-1864) there were other rebellions in China as well.
Nian Rebellion (1851-1868) in north China
Red Turban Rebellion (1854-1856) in Guangdong
Miao Rebellion (1854-1873) in Guizhou
Panthay Rebellion (1856-1873) in Yunnan
Dungan Revolt (1862-1877) along the western bank of the Yellow River
These rebellions fed off one another. If the Manchu move troops out of region to fight in another, it made that first region more likely to rebel. Likewise, they increased taxes to pay for the troops to fight the rebels, causing that area to become more prone to rebel.
China in this time was in a rebellious mood. Leadership is important, but even without Hong Xiuquan there are other leaders willing to step forward. Hong Xiuquan was the most successful of the rebel leaders, but he was not able to unify all the rebels fighting the Qing at this time.
Without Hong Xiuquan, the period of mass rebellions might be put off for a decade or so. However, that is just keeping the lid on the pot longer, building up steam.
There will be a mass rebellions against the Qing. However, with butterflies we don't know if it will be less or more successful than the Taiping. The Qing could very well survive as in our timeline, or they may end up falling if more of the elite defect to the rebels and drive out the Manchu and establish a new dynasty like the Ming did (although they will have many of the same problems the Qing had). Or it could lead to something like the warlord era where different parts of China had their own governments).